Neutronic reactor shield and spacer construction



Nov. 185 1958 E. P. WIGNER ETAL 2,851,034

NEUTRCNIC NEACTOR SHIELD NND SPACER CONSTRUCTION Filed Sept. 18. 1945 4 Sheets-Sheet 1 4 Sheets-Sheet 2 *A E. P. WIGNER ETAL NEUTRONIC REACTOR SHIELD AND SPACER CONSTRUCTION Nov. 18, 1958 Filed sept'. 18, 1945 Nov. 18, 1958 E. P. WGNER ETAL 2,861,034

NEuTRoNIc REAcToR SHIELD NND SPACER CONSTRUCTION Filed Sept. 18, 1945 4 Sheets-Sheet 3 FIELE- fizesses: ZZ/en' Z'o ws:

Nov. 18, A1958' E. wlGNER ETAL 2,861,034

NEUTRONIC REACTOR SHIELD AND SPACER CONSTRUCTION Filed Sept. 18, 1945 4 Sheets-Sheet 4 ATTORNEY United States Patent NEUTRONIC "lREr-iJCTIlR` SHIELDAND SPACER CONSTRUCHN;

Eugene P'. `Wigner and Leo A..0hlinger, Chicago, Ei., as*I signors to` the .UnitedStates of 'America as represented by the, United 'States Atomic. llnergy,` Commission Application September18,1945,` Serial N o. 617,123.`

l'Cliin. (Cl."204f-193.2)

ofcompositions containing such` iissionable material, for.

example,` natural luranium,L disposed iny a neutron `slowing materialtwhich slows the. neutrons to thermal energies..

Such a slowing material isterrned a neutronmoderator. Carbon and-D2O (heavywater) are typical moderators suitable forsuch use. Heat is evolved duringrthe reaction which is removed. by passage of a coolant thro-ugh the reactor in: heat exchange relationship therewith. Specific.

details .ofthe theoryfand essential characteristics of such reactors arerset 'forth in; Fermi et al. Patenti` 2,708,656, issued `May 17, 1955, and the copending Creutz et al. application,.Sria1...Number 574,153, led January 23, 1945..

As.. is stated...above, ,in` the operation of a. neutronic reactor. heat `is evolved during .thereactionwhich is removedby passage of a coolant through the reactor in heatexchange relationship with `the active materials. In.

reactors of the typesuch as that disclosed in. Figs. through 7` of the. latter .application referredto. above, the issionable material is loadedA into channels opening into one faceoflthe reactorand a-coolant,. such-as water, is introduced. into the` channels from the same'ace. lt is manifest that. suitable shielding units or plugs will be re-` quired inthe. .channels between` the outermostbodiesof iissionable material andtheface of the reactor into which the channels open, since operating personnelY mustlbe shielded from the harmful emanations of. the reactive portion. of4 the reactor. The plugs heretofore used .have provedunsatisfactory, particularly rdueto causing a serious .drop in the. pressure of the passing. coolant., The present` invention overcomes existing ditiiculties in the provision of. novel. `spacing plugs disposed between improved shieldingV plugs;

Therefore, it is an .object ofthe present invention to provide a novel spacing plug which is adaptedV to be used in thercoolant channel` of` a -neutronic reactor.

Another object is toE provide a .novel shielding. and.

spacing construction for the coolant channel of-,a neutronic reactor.

Another` object is tto. provide a novel` spacing device adapted for. usein the coolant channelA of a neutronic reactor which is constructed toeffect a minimum. pressure drop in a passing coolant and which remains substantially stationaryin the coolantchannel during passage of coolant.

The foregoing and other objects and advantages are apparent from the following description read with reference to the accompanying drawings, in which:

Fig; lV is adiagrammatic fragmentaryvertical crosssectional view, partlyy in elevation, through the reactive portion and the loading structure of a neutronic reactor;

Fig. 4 is an enlarged elevational view ofthe spacing` plug shown in Fig. 2;

Fig. 5 is an end View.. of the spacingL plug, shown in-v Fig. 4;

Fig. 6 is an enlarged cross-sectional'view taken on.the line 6 6 .of Fig. 2;

Fig. 7 is a longitudinal.cross-sectional'view through a. modified spacing plug;

Fig. 8 is a cross-sectional view taken on thelinev 8"-8 of Fig. 7; and

Fig. 9 is a schematicdiagram showing the external circulating system for the coolant of the reactor.

Referring to the drawings, there issh'own diagrammaticallyin Fig. 1 `a neutronic reactor 20 of the type with` which the present invention finds particular application and which. is described in detail in the above-mentioned.` copending applications. Broadly, the neutronic reactor 20 includes a supportingbase 22. of concrete, arvertical concrete wall 24 extending from the foundation 22and` forming three sides of a large-enclosure, .and a steel Vshot and water shield .26. forming `the fourthside of.the .enclosure. Exteriorly of and. adjacentto the shield 26`is a shield 28 comprising steel chamber-dening plates enclosing lead Wool orshot. Within the enclosure. just de-.. scribed is a reactive portion 3ll`which comprises graphite moderator .material 32 within whichis disposed a` plurality of tubes or channels 34 which extendrthrough` the shields 26 and 2S in one direction and open into a. chamber containing. coolant water36 at the other ends. A charging or loading structure 38 .is disposed radjacent the shield 28. If the reactor is located neararelatively pure bodyof. water, such as a river of suiicient size to, supply the necessary` quantity of water. to extract the. required .amount of heat, then this river water can be passed may` carry with tcertain free4 gases, suchas hydrogen` and oxygen, if water is used, which should be eliminated from the` cooling circuit. For this purpose, the coolant leaving the reactor is passed through a` ilashtank where` these gases are removed. The coolant is then cooled,`

and finally pumped back through the reactor and recir-'I culated.

In Fig'. 9, the reactor is diagrammatically shown at 20, the water inlet header being illustrated`1`i` The cooli ing water is discharged from the reactor into the vertical chute 128, and then enters the pipe 141 through which it is conveyed by pump` 1Mb to a flash tank 142, after" passing through a throttling valve 141e. Thewater leavesL the ash tank 142 through pipe 143, passes throughheat:

exchanger 144 where it is cooled by owing in heat-` exr` change relationship with a cooler liquid, and `then flows through pipe 145 and. is returned to the rreactor-20-bythe pump 145 through pipe 147.

The water entering the heat exchanger 144 has a` temfV perature only slightly less than the boiling` point :at .the

existing pressure. The waier leaving theheat exchanger.

144 has a temperature of about 95 Fl, lthis cooling be-l Patented Nov.. 18, 1951i` i ing accomplished by transferring the heat to the cooler uid in a secondary cooling system.

This secondary cooling system includes a cooling tower kgenerally illustrated at 154, a pump 155, the heat exchangerv144 and' suitable piping 156. The cooling iluid in the cooling tower 154, and for purposes of illustration water has been selected for this uid, is collected in a reservoir157 at the bottom of the tower from which the Water is'withdrawn by pump 155 and passed to the heat exchanger 1,44. This water entering the heat exchanger 144 is atV a temperature of about 85 F. and leaves the heat exchanger at a temperature of about 130 F. This hot water passes through pipes 156 into spray head 158 disposed adjacent to the top of the cooling tower 154. The hot water is sprayed in a fine mist into the cooling tower 154, and 4mixes with air circulated through the cooling tower by a blower 159. Evaporation takes place resulting in the cooling of the water in the cooling tower 154 so that the water collected in the reservoir 157 has been electively cooled by this process of evaporation.

Losses due to vaporization may be replaced as will be` vided with radiation shielding to protect personnel from the harmful effects of gamma radiations. As shown, the flash tank 142 is surrounded by a cylindrical concrete wall 164 extending above the top of the flash tank 142 and forming an enclosure which is completely lled with water. A similar wall 165 surrounds the heat exchanger 144, and the tank formed therebyl likewise is iilled with water. For purposes of illustration, only a diagrammatic showing is made at 166 of a shield surrounding the reactor 20. More complete details of this latter shield are brought out in the description of the reactor itself. For further details of the reactor 20 the disclosures of the above-identiiied -copending applications are hereby incorporated by reference.

Referring to Figs. 2 and 6, one channel 34 is disclosed on an enlarged scale. The channel 34 includes longif tudinal ribs 40 which support abutting bodies 42 of fissionable material in the reactive portion 30, and spacing plugs 44 and shielding plugs v46 in the rellector portion 48`of the reactive portion 30 and in the shields 26 and 28, as shown. The abutting bodies 42 are disposed within the channels 34 in the graphite moderator except in those portions of the channels in the moderator that are adjacent that part of the shield 26 through which the channels 34 extend. The spacing plugs 44 are in those portions of the channels 34 and also in certain portions of the channels 34that extend throughthe shield 26. The section of the graphite moderator that contains the aforementioned channel portions which are beyond the bodies v,'42 is the reflector portion 48. The ribs 40 in each channel 34 constitute means inside each channel for spacing the shielding elements 46 therein from the inside of the channel.V A coolant 41, such as Water, ows between the bodies 42 and the interior of the channel 34.

In Fig. 3vr the shielding plug 46 is shown in detail and includes a cylindrical body 50 of lead or steel, or other gamma ray and neutron absorbing material, having a reduced blunt nose portion 52 to ease the coolant How. Thus the body 50 is constructed of material having high neutron and radiation absorption cross sections. The body 50 is disposed in an aluminum sheath 54 which is suitably sealed at the end remote from the nose portion 5-2, the disclosed seal comprising a double weld. The ends of the shielding plug 46 form planes at substantially right-angles to the longitudinal axis of the body 50 to insure firm abutting relationship with adjacent plugs when disposed in the channel 34.

In Figs. 4 and 5 a preferred embodiment of the spacing plug 44 is shown in detail. The plug 44 includes a strong solid central rod 58 to which is secured two spiral ribs or iins 60, which wind in opposite directions about the rod. The plug 44 may be cast as an integral unit or the ribs 60 may be secured in anysuitable manner to therod 58. Aluminum is a preferred material 'for the'plug 44.

In Figs. 7 and 8 there is disclosed a modified spacing. plug generally designated 64. The spacing plug 64 in` cludes a central solid rod 66 and a -cylindrical portion 68 secured to the rod 66 by four substantially equally spaced ribs or fins 70. The rod 66 is offset longitudinally with respect to the cylindrical portion 68 and the ribs 70 are undercut at both ends in respect to the cylindrical portion 68, as is clearly shown in Fig. 7. When the plug 64 is disposed in a channel 34 it is not essential that the ribsv 70 align, although vsuitable notching means, or the like,`

may Ibe providedl to effect alignment if desired.

As is shown in Fig. 2, one preferred disposition lof shielding plugs 46 and spacing plugs 44 in respect to the type of neutronic reactor 20 disclosedherein contem-v plates a pair of shielding plugs 46 disposed within-the shield 26 adjacent the reactor portion 30 to absorb a substantial portionl of the primary gamma rays following the'Y channel 34 as an exit path, and a second pair of shielding plugs 46 disposed in the shield 28 adjacent the charging Between j the pairs of shielding plugs 46, between the inner pair of shielding plugs 46 and the ssionable bodies 42, and', outwardly of the Vouter pair of shielding plugs 46 are'k disposed spacing plugs 44. The spacing plugs 44 and f side thereof to absorb secondary gamma rays.

the shielding plugs 46 are supported by the ribs 40.

A coolant medium such as water is introduced into the channels 34 adjacent the charging ends and passes be.

tween the shielding plugs 46 and the inner surfaces of the channels 34 and through the passageways provided by the reverse spirals of the spacing plugs 44. Inasmuch as there is no great restriction of thecoolantflowjthrough the spacing plugs 44 the pressure drop of the coolant inV passing the spacing plugs 44 is' very small, an importantY ,j advantage since the maximum amount of pressure which" can be applied to the coolant for forcing it through thev reactive portion 30 is limited by a number of factors which are set forth in the above-identified copending applications. Furthermore, the oppositely directed ribs 60. Y on each of the plugs 44 prevent the rushing coolant from,

rotating the plugs in the channels 34, an action which would damage either the plugs 44 or the channels 34, or

both, and which would give an undesirable swirling action to the coolant.

The same advantages obtain for the spacing plug 64 as for the spacing plug 44. It is to be understood that the plugs 64 are disposed in coolant channels in the same manner as plugs 44 when operatively employed. Both plugs have suicient structural strength to permit their use as cumulative ram rods in charging the coolant channels with ssionable material if such is desired.

While the theory of nuclear reactions set 'forth herein t is based on the best presently known experimental evidence, the invention is not limited thereto, as additional' experimental data later discovered may modify the theoryv E.' p l disclosed.

Obviously, many modilications may be made inthe;` specific plug embodiments and in the disposition of the j, j 'If' shielding and spacing plugs disclosed without departing from the intended scope of the invention.

What is claimed is:

A neutronic reactor comprising a graphite moderator L'. provided `with a plurality of channels therethrough, a shield disposed about the moderator, the channels extending through the shield, a plurality of abutting bodies of. uranium disposed within the channels in the graphite moderator except ,int those portions of the channels in the,

moderator that are adjacent that part of the shield through which the channels extend, a plurality of spacer elements disposed within saidI outer portions of the channels in the graphite moderator, each spacing element comprising a solid rod member and a pair of ribs winding about said member in opposite directions, shielding elements constructed of material having high neutron and radiation absorption cross sections disposed within the channels traversing the shields within the reactor, means inside each channel for spacing the shielding elements therein from the inside of the channel, and means to ow uid coolant through the channels.

Davis Feb. 2o, 1866 6 Hendrich Sept. 12, 1905 Roberts et al. Sept. 3, 1907 Carroll Apr. 7, 1908 Andrews July 20, 1909 Steynis Oct. 17, 1916 Willson et al June 19, 1917 Allison Feb. 24, 1920 Robe May 1, 1923 Mueller July 22, 1924 Welsh Aug. 8, 1933 FOREIGN PATENTS Switzerland Oct, 2, 1944 

